rfc/signon_error_log is a SAP Parameter attribute which is used to control Ausgabe von Informationen bzgl. misslungener RFC-Anmeldung information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
In order to receive additional information on the cause of the login
problem in the form of an ABAP short dump when an RFC logon fails or not
to receive short dumps for compatibility reasons, you must include the
profile parameter "rfc/signon_error_log" into the pfile file of the
relevabt application server.
When setting the profile value to 0 (that is, rfc/signon_error_log = 0)
no ABAP short dump is written but only a syslog entry is created.
When setting the profile value to 1 (that is, rfc/signon_error_log = 1),
the short dump "CALL_FUNCTION_SIGNON_REJECTED" is displayed for every
logon error. The content of this dump can be analyzed using the ABAP
short dump analysis transaction (transaction code: ST22).
When setting the profile value to -1 (that is, rfc/signon_error_log =
-1), an ABAP message is displayed for every logon error instead of the
short dump. This is the default setting.
Value 0 =
Inactive
1 =
Short dump active
2 =
Short dump active and trace outputs in developer trace files (dev_w*)
-1 =
No short dump active but ABAP message and trace outputs in developer
trace files (dev_w*)
See SAP Parameter Documentation for full SAP documentation for this profile parameter.